1. Field of the Invention
The present invention relates to a structure of a cylinder block.
2. Description of the Related Art
Generally, a skirt portion, the lower structure of a cylinder block for an engine (an internal combustion engine), forms a crankcase to contain a crankshaft.
For example, an accompanying drawing FIG. 8 schematically illustrates a cylinder block for an engine (a V-engine) seen from the axis direction of a crankshaft. As shown in FIG. 8, a crankshaft 3 is arranged inside a skirt portion 2 of the cylinder block 1. The crankshaft 3 is mounted, via bearings (bearing metals, not shown), on bearing mechanisms 4 formed in the cylinder block 1 and bearing caps 5 are attached to bottom of the bearing mechanisms 4 in order to fix the bearings of the crankshaft 3. The bearing mechanisms 4 are placed at both ends and appropriate intermediate portions of the engine. A bearing cap 5 is mounted on each of the bearing mechanisms 4.
In order to fasten the bearing caps 5 to the cylinder block 1, beams 6 in the separated form from the bearing caps 5 are attached one to each bearing cap 5. Each beam 6 is disposed at the skirt portion 2 of the cylinder block 1 in such a direction that the beam 6 extends in the crosswise direction (perpendicular to the crankshaft 3) of the engine. The both end of each beam 6 is fixed to the skirt portion by bolts 7 and the intermediate portion between the both ends is fixed, together with the corresponding bearing cap 5, to the bearing mechanism 4 by longer bolts 8.
An oil pan (however not shown) is arranged under the skirt portion 2 (under the beams 6) of the cylinder block 1 and store a drain of an engine oil serving as a lubricant in the cylinder block 1. Further, a baffle plate is placed between the top of the oil pan and the bottom of the beams 6.
In relation to a technique concerning a skirt portion in such a cylinder block, for example, Japanese Patent Laid-Open (KOKAI) Publication Number 2000-104726 discloses a structure in which height between the top surface and the bottom surface of each bearing cap is set equal to the height between the cap-installation surface and the bottom surface of each skirt portion and a ladder board connects the bottom surfaces of each adjacent pair of the skirt portions. The fringe of each ladder board is fixed to the bottom surfaces of the corresponding skirt portions by oil-pan bolts and is fastened to the cap-installation surface of the cylinder block via a bearing cap by cap bolts, so that the ladder boards, the bearing caps and the cylinder block are formed into an integrated body.